Diff the output of two only slightly different commands. I got annoyed.

diffcmd.py

#!/usr/bin/env python3

# Assumes that the differing argument is the last one.

import argparse
import os
from pathlib import Path
import shlex
import shutil
import subprocess
import sys
import tempfile

def logcmd(s):
    text = s if isinstance(s, str) else shlex.join(s)
    return print(f'{text}\x1b[0m', file=sys.stderr)

parser = argparse.ArgumentParser()
parser.add_argument('-d', '--differ', default=os.environ.get('DIFF', 'diff'))
parser.add_argument('template', nargs=argparse.REMAINDER, type=str,
    help="% gets replaced with 'before' and 'after', and each is run as a command",
)

args = parser.parse_args()

with tempfile.TemporaryDirectory() as tmpdir:
    temp_path = Path(tmpdir)

    template_args = args.template
    template_args[0] = shutil.which(template_args[0]) or template_args[0]

    first_args = [arg.replace('%', 'before') for arg in template_args]
    second_args = [arg.replace('%', 'after') for arg in template_args]

    first_output = subprocess.check_output(first_args)

    logcmd(second_args)
    second_output = subprocess.check_output(second_args)

    first_path = temp_path / 'first.out'
    second_path = temp_path / 'second.out'

    with first_path.open('wb') as first_out:
        first_out.write(first_output)

    with second_path.open('wb') as second_out:
        second_out.write(second_output)

    diff = shlex.split(args.differ)
    diff[0] = shutil.which(diff[0]) or diff[0]

    diff_args = [*diff, first_path.as_posix(), second_path.as_posix()]
    logcmd(diff_args)
    subprocess.call(diff_args)